For nearly a century now, the most popular form of residential energy has been electricity owing to its convenience. Electricity lights our houses and powers most all of our household appliances merely by connecting a plug into a wall socket.
But how does electricity work?
Electricity is based on the flow of tiny charges (electrons) through a metal wire.
To make the electrons move, work must be done either by a battery (chemical energy) or a generator (kinetic energy) to "pump" the electrons through the wire. The pumping of electrons is analogous to the pumping of water uphill through a pipe. The pumping produces potential energy that can be transferred into useful work such as lighting a light bulb or heating a toaster.
Notice that the electrons, like the water, travel a closed path or circuit.
Neither the water nor the electrons are "used up". Instead, work is input to push each around the circuit and, aside from some heating in the wire, that work reappears in the production of another form of energy in whatever device (light bulb, toaster, etc.) that is placed into the circuit.
In the example shown above, the chemical energy of a battery pushes electrons around a circuit that includes a light bulb. The filament of the light bulb is a narrow passageway in the circuit where the electrons are squeezed through. As they push through, their friction causes the filament to glow because of the heat this generates and produces light (another form of energy).
Again, the electrons are never "used up". They are merely pushed around the circuit. So, when we buy "electricity," we don't buy the electrons. Instead, we buy the potential energy they have as a result of the power company pushing them through our appliance.
AC and DC
There are two forms of electricity:
DC (direct current) - in DC electricity the electrons are pushed at a steady rate in one direction only.
This is commonly the situation for a battery where electrons are pushed from the negative terminal toward the positive terminal.
AC (alternating current) - in AC electricity the electrons are pushed in alternating directions - first one way, then the other.
This is the sort of electricity found in most households in the U.S. where the direction is switched about 60 times every second (or 60 Hertz)!
Although AC electricity is available at most household wall sockets, many modern appliances require DC current to operate.
In these instances it is common to find AC-to-DC converters or adapters like the ones illustrated which convert the alternating current flow into a direct current.
An excellent illustration of the differences between DC and AC current is available at the following website: